1. Field of the Invention
The invention relates generally to integrated circuits, and more particularly to controlling a voltage in a DC/DC converter.
2. Description of Related Art
Conventional DC/DC converters have a pin available that allows the adjustment of the supply output. When this pin is left unconnected, the voltage output will be at the nominal setting for the converter within a certain tolerance set by the manufacturer. During testing of a system using these converters, it is common to run tests at this nominal voltage and at a lower and a higher voltage to ensure that the components being powered by the converter are not marginal. This is generally accomplished by placing a is resistor between the supply output and the trimming pin or the trimming pin and ground.
The value of the resistor will determine the voltage difference between nominal and the test voltage.
At the conclusion of a test, the trimming pin is left unconnected. The problems with this approach are: the nominal voltage output may not be as accurate as the system requires, changing the voltage difference for testing requires a resistor change, the accuracy of the output voltage is unknown due to the difficulty in obtaining exact resistor values and the unknown nominal output value of the converters, and switches are required to connect and disconnect the resistors. The resistors and switches are duplicated for each DC/DC converter in a system.
Accordingly, it is desirable to have a system and method for precisely controlling the voltage at the output of a DC/DC converter.